Brassica napus L. is a vegetable oil crop, commonly known as rapeseed (or canola). It is widely used as a source of oil and protein for food and industrial applications, but also as a remedy, and in a field of attraction or as an ornament due to its diverse flower colors. Every part of rapeseed is useful, even the waste, which could be used to feed animals, or recycled. In this review, the use of rapeseed in these applications is presented, starting with the preparation of oil and protein from the seeds, before their release in the market, to the utilization of natural unprocessed rapeseed. Progress in rapeseed exploitation for food, remedy, energy source, and industrial applications are analyzed to show variability in diverse findings, to provide insights and progressive descriptions of rapeseed usage to other scholars. Moreover, advancements in breeding for rapeseed improvement were described. In the future, strategies could be developed or improved to avoid or decrease crop losses, but also to increase interest in propagating the valuable traits of rapeseed.

Late embryogenesis abundant (LEA) proteins are a diverse and large group of polypeptides that play important roles in desiccation and freezing tolerance in plants. The LEA family has been systematically characterized in some plants but notBrassica napus. In this study, 108BnLEAgenes were identified in theB. napusgenome and classified into eight families based on their conserved domains. Protein sequence alignments revealed an abundance of alanine, lysine and glutamic acid residues in BnLEA proteins. TheBnLEAgene structure has few introns (<3) and they are distributed unevenly across all 19 chromosomes inB. napus, occurring as gene clusters in chromosomes A9, C2, C4 and C5. More than two-thirds of theBnLEAgenes are associated with segmental duplication. Synteny analysis revealed that mostLEAgenes are conserved, although gene losses or gains were also identified. These results suggest that segmental duplication and whole-genome duplication played a major role in the expansion of theBnLEAgene family. Expression profiles analysis indicated that expression of mostBnLEAs was increased in leaves and late stage seeds. This study presents a comprehensive overview of theLEAgene family inB. napusand provides new insights into the formation of this family.

Summary: Drought is an abiotic stress that affects plant growth, and lipids are the main economic factor in the agricultural production of oil crops. However, the molecular mechanisms of drought response function in lipid metabolism remain little known. In this study, overexpression (OE) of different copies of the drought response genes LEA3 and VOC enhanced both drought tolerance and oil content in Brassica napus and Arabidopsis. Meanwhile, seed size, membrane stability and seed weight were also improved in OE lines. In contrast, oil content and drought tolerance were decreased in the AtLEA3 mutant (atlea3) and AtVOC‐RNAi of Arabidopsis and in both BnLEA‐RNAi and BnVOC‐RNAi B. napus RNAi lines. Hybrids between two lines with increased or reduced expression (LEA3‐OE with VOC‐OE, atlea3 with AtVOC‐RNAi) showed corresponding stronger trends in drought tolerance and lipid metabolism. Comparative transcriptomic analysis revealed the mechanisms of drought response gene function in lipid accumulation and drought tolerance. Gene networks involved in fatty acid (FA) synthesis and FA degradation were up‐ and down‐regulated in OE lines, respectively. Key genes in the photosynthetic system and reactive oxygen species (ROS) metabolism were up‐regulated in OE lines and down‐regulated in atlea3 and AtVOC‐RNAi lines, including LACS9, LIPASE1, PSAN, LOX2 and SOD1. Further analysis of photosynthetic and ROS enzymatic activities confirmed that the drought response genes LEA3 and VOC altered lipid accumulation mainly via enhancing photosynthetic efficiency and reducing ROS. The present study provides a novel way to improve lipid accumulation in plants, especially in oil production crops.

High-density linkage maps can improve the precision of QTL localization. A high-density SNP-based linkage map containing 3207 markers covering 3072.7 cM of the Brassica napus genome was constructed in the KenC-8 × N53-2 (KNDH) population. A total of 67 and 38 QTLs for seed oil and protein content were identified with an average confidence interval of 5.26 and 4.38 cM, which could explain up to 22.24% and 27.48% of the phenotypic variation, respectively. Thirty-eight associated genomic regions from BSA overlapped with and/or narrowed the SOC-QTLs, further confirming the QTL mapping results based on the high-density linkage map. Potential candidates related to acyl-lipid and seed storage underlying SOC and SPC, respectively, were identified and analyzed, among which six were checked and showed expression differences between the two parents during different embryonic developmental periods. A large primary carbohydrate pathway based on potential candidates underlying SOC- and SPC-QTLs, and interaction networks based on potential candidates underlying SOC-QTLs, was constructed to dissect the complex mechanism based on metabolic and gene regulatory features, respectively. Accurate QTL mapping and potential candidates identified based on high-density linkage map and BSA analyses provide new insights into the complex genetic mechanism of oil and protein accumulation in the seeds of rapeseed.

Increasing seed oil content is one of the most important goals in breeding of rapeseed (B. napus L.). To dissect the genetic basis of oil content in B. napus, a large and new double haploid (DH) population containing 348 lines was obtained from a cross between ‘KenC-8’ and ‘N53-2’, two varieties with >10% difference in seed oil content, and this population was named the KN DH population. A genetic linkage map consisting of 403 markers was constructed, which covered a total length of 1783.9 cM with an average marker interval of 4.4 cM. The KN DH population was phenotyped in eight natural environments and subjected to quantitative trait loci (QTL) analysis for oil content. A total of 63 identified QTLs explaining 2.64–17.88% of the phenotypic variation were identified, and these QTLs were further integrated into 24 consensus QTLs located on 11 chromosomes using meta-analysis. A high-density consensus map with 1335 marker loci was constructed by combining the KN DH map with seven other published maps based on the common markers. Of the 24 consensus QTLs in the KN DH population, 14 were new QTLs including five new QTLs in A genome and nine in C genome. The analysis revealed that a larger population with significant differences in oil content gave a higher power detecting new QTLs for oil content, and the construction of the consensus map provided a new clue for comparing the QTLs detected in different populations. These findings enriched our knowledge of QTLs for oil content and should be a potential in marker-assisted breeding of B. napus.

Background: Brassica napus is one of the most important oilseed crops, and can supply considerable amounts of edible oil as well as provide raw materials for the production of biodiesel in the biotechnology industry. Lysophosphatidic acid acyltransferase (LPAT), a key enzyme in the Kennedy pathway, catalyses fatty acid chains into 3-phosphoglycerate and promotes further production of oil in the form of triacylglycerol. However, because B. napus is an allotetraploid with two subgenomes, the precise genes which involved in oil production remain unclear due to the intractability of efficiently knocking out all copies with high genetic redundancy. Therefore, a robust gene editing technology is necessary for gene function analysis. Results: An efficient gene editing technology was developed for the allotetraploid plant B. napus using the CRISPR-Cas9 system. Previous studies showed poor results in either on-target or off-target activity in B. napus. In the present study, four single-gRNAs and two multi-gRNAs were deliberately designed from the conserved coding regions of BnLPAT2 which has seven homologous genes, and BnLPAT5, which has four homologous genes. The mutation frequency was found to range from 17 to 68%, while no mutation was observed in the putative off-target sites. The seeds of the Bnlpat2/Bnlpat5 mutant were wizened and showed enlarged oil bodies, disrupted distribution of protein bodies and increased accumulation of starch in mature seeds. The oil content decreased, with an average decrease of 32% for Bnlpat2 lines and 29% for Bnlpat5 lines in single-gRNA knockout lines, and a decline of 24% for Bnlpat2 mutant lines (i.e., g123) and 39% for Bnlpat2/Bnlpat5 double mutant lines (i.e., g134) in multi-gRNA knockout lines. Conclusions: Seven BnLPAT2 homologous genes and four BnLPAT5 homologous genes were cleaved completely using the CRISPR-Cas9 system, which indicated that it is effective for editing all homologous genes in allotetraploid rapeseed, despite the relatively low sequence identities of both gene families. The size of the oil bodies increased significantly while the oil content decreased, confirming that BnLPAT2 and BnLPAT5 play a role in oil biosynthesis. The present study lays a foundation for further oil production improvement in oilseed crop species.